Hi - perhaps see my reply to the similar question about Discord here: Discord Webhooks - #2 by mig5
To use Taiga webhooks, the other side (receiving the payload) must know already how to parse the payload format and use the information it delivers. So it’s more designed for if you are writing the consuming app on the other side and can customise it to understand Taiga’s payload.
If a third party service (in this case Synology Chat) doesn’t have any built-in understanding of the payload that a Taiga webhook delivers, it won’t work.
If you can’t configure Synology Chat to understand the Taiga webhook payload, you need to approach it from the opposite angle: by writing a Taiga-native plugin that sends event data in the format that Synology expects. This is how the Slack plugin works, for example, and why it isn’t configured as a generic ‘Webhook’ but is its own plugin - same with the Github integration.